I'm using the Arduino Mega to read inputs from multiple sensors. Currently I have a total of 35.45 mA being pulled out of the 5V supply pin. I'm wondering if I need to add up to two more sensors what the max Amps that are able to be pulled from that 5V supply pin? Is it 40mA total? If it cannot should I run the extra sensors through the digital output pins?
Also can the Arduino handle an additional 4-20mA pull into one of the analog input pins?
The analog Input pins will only accept 1uA (microAmp) of current. They are very high impedance inputs, a charactertistic of CMOS.
The 5V rail can supply up to 800mA for the entire board if powered by the barrel jack, and the input voltage is not very high, say 7.5V. Approaching 800mA the 5V regulator is likely to overheat, and <800mA with higher voltage input.
500mA is the limit for the entire board if powered from the USB port.
The board itself will draw in the neighborhood of 50mA. Two35mA loads should not be an issue.
Do not use an Output pin and expect to see >4.2V when >=20ma are being sourced.